1. Field of the Invention
The present invention is related to printers and more particularly print head assemblies of printers.
2. Description of Related Art
Controlling printing quality often requires proper, accurate registration between a print head and the underlying printer media. Such registration can be difficult to maintain with variations in printer media, including the thickness of the printer ribbon and printer label or paper stock.
A conventional printer 10, such as shown in FIGS. 1 and 2, typically includes a printer frame 11 supporting a media supply 12, a ribbon supply 13, a platen assembly 17 and a print head assembly 14. The media supply can include a compartment 15 of paper, labels or other media, that is in a positioned generally above and upstream (with respect to movement of the media) of the print head assembly 14. The ribbon supply 13 includes a supply spool 24 that supplies a printer ribbon extending through the print head assembly 14 and onto a takeup spool 16. Both of the spools 14, 24 are rotatably supported by the printer frame 11. The platen assembly 17 includes a platen roller 18 that is rotatably supported by the printer frame 11 subjacent the print head assembly 14.
As shown in FIG. 2, the print head assembly 14 of the conventional printer 10 includes a print head ceramic base 19, an aluminum heat sink 20 and a pressure spring 21. The ceramic base 19 includes a print line which is a heating element that is selectively heated to pass ink from a ribbon or to directly thermal print onto the paper, label or other printable media. Supporting the print head ceramic base 19 is the heat sink 20 which itself is supported by a bracket 22. Ends of the bracket are rotatably supported by the printer frame 11, thereby allowing rotation of the heat sink 20 and the print head ceramic base 19 relative to the platen roller 18.
The print head assembly 14 of the conventional printer 10 also includes the pressure spring 21 that has a V-shape, as shown in FIGS. 1 and 2. The ends of the V-shape are supported by the printer frame 11 proximate ends of the rotatably supported bracket 22 and the pressure spring 21 extends downward onto a middle line of the bracket. In particular, the center of the V-shape has a line of contact due to the spring 21 being constructed of a ribbon of sheet metal that exerts a torque to control angulation as well as a downward bias on the bracket 22. These biases help to maintain contact of the ceramic base 19 and its print line with the ribbon and printer media passing between it and the platen roller 18.
Although helping the ceramic base 19 to maintain contact with the printer media and platen roller 18, the V-shaped pressure spring can interfere with passage of the media. Also, improvements in the ability of the print head assembly 14 to track the media are always desired.
Therefore, it would be advantageous to have a printer assembly that provides clearance for passage of media in a printer but still follows the media with accuracy for overall improved printing capability.